The overall objective of these studies is to investigate the degree of tumor localization by certain biologically significant compounds labeled with relatively short-lived radionuclides. Certain labeled compounds will be evaluated as agents for early detection of cancer, and employed in studies of normal and abnormal metabolism. These cyclotron-produced radionuclides have short half-lives which greatly reduce patient exposure, but require detection apparatus suitable for high-energy radiation. These studies will be evaluated in animals and man with quantitative scanning and imaging systems. Specific proposed studies: (1) Evaluation of Diphenylhydantoin-11C as a Brain Scanning Agent. (2) Evaluation of Valine-11C as a Pancreatic Scanning Agent. (3) Nitrogen-13 Compounds for Tumor and Organ Localization in Human Cancer patients. (4) Preparation and Evaluation of 13N-Nitroso Compounds and 18F-Haloperidol as Diagnostic Scanning Agents. (5) Studies of 73Se Compounds for Tumor Localization in Animal Models and in Human Cancer Patients.